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1 A Distributed Delay-Constrained Dynamic Multicast Routing Algorithm Quan Sun and Horst Langendorfer Telecommunication Systems Journal, vol.11, p.47~58, 1999
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2 Outline Motivation Network model and problem definition DCR algorithm DCDMR algorithm Performance evaluation Conclusion
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3 Motivation Problem –Multicast group members always change frequently –Few delay-constrained multicast routing algorithm support dynamic groups –Most existing dynamic routing heuristics only consider one link metric
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4 Motivation (cont) Objective –Find a dynamic multicast routing algorithm with characteristics : Accommodate members change Satisfy end-to-end QoS requirement Efficient network resource utilization Scale well
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5 Outline Motivation Network model and problem definition DCR algorithm DCDMR algorithm Performance evaluation Conclusion
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6 Network Model Given –Connected, directed graph G(V,E) –Associated with each asymmetrical link Delay D(e) Cost C(e) –Source node s ( ) –Set of destination S ( ) –Delay tolerance
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7 Problem Find –A tree T ( ) rooted at s and span all nodes in S satisfying – is minimum –
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8 Model of Dynamic Routing Problem Given –Directed network G(V,E) –Non-negative link metric with Link costs C and link delays D –Delay tolerance –Initial delay-constrained tree with source s ( ) –Series requests
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9 Dynamic Problem Find –A series of delay-constrained multicast tree Members of T i are T 0 modified by requests Cost of T i is minimum of all possible T i
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10 Outline Motivation Network model and problem definition DCR algorithm DCDMR algorithm Performance evaluation Conclusion
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11 Routing Information Each node –Know delay of all outgoing links –Maintain a delay and cost vector with |V|-1 entries Assume delay and cost vectors do not change during execution routing algorithm
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12 Delay and Cost Vector Entry for in delay vector of –Destination ID : –End to end delay : –Cost of least delay path : –Next hop of on : Entry for in cost vector of –Destination ID : –End to end delay : –Cost of least cost path : –Next hop of on :
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13 Delay-Constrained Unicast Routing Algorithm (DCR) Objective –Construct a low-cost path from s to d satisfying given delay bound Idea –First check if –Always try to along least cost path toward d if –until d is reached
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14 DCR Algorithm If exit True If False Next_node= path_direction=LC path_construction=(d,LC) True False Next_node= path_direction=LD delay_so_far= path_construction=
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15 DCR Algorithm (cont) If Successful construct path False True If Path_direct=LC or delay_so_far+ False Next_node= path_direction=LD delay_so_far= delay_so_far + path_construction= Next_node= path_direction=LC path_construction=(d,LC) True
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16 Example of DCR algorithm A C B D E (30,1) (20,2) (10,1) (10,2) (30,1) Source node : A Destination node : E Delay bound : 5 (cost,delay) pair with each link A C E D B (30,1) (10,2) (10,1) (20,2) A C E D B (10,1) (30,1) (10,2) (10,1) A C D E B (20,2) (30,1) (10,2) (10,1)
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17 Outline Motivation Network model and problem definition DCR algorithm DCDMR algorithm Performance evaluation Conclusion
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18 Delay-Constrained Dynamic Multicast Routing (DCDMR) DCDMR –Based on DCR algorithm – denote delay of unique path from s to on existing tree T Idea of FAST mode –New member contacts on tree node with request (,mode) along least delay path
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19 DCDMR with FAST Mode and If False exit If True False Send Req to v p ’s parent Use DCR to compute a path from v p to v n satisfying constraint True
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20 DCDMR with SLOW Mode If and False exit True If False Send Req to v p ’s parent True If True Rsp=(v n,SLOW,v p, ) and send to all v p ’s neighbors False Rsp=(v n,SLOW,v p, ) and send to all v p ’s neighbors
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21 DCDMR with SLOW Mode (cont) If False Send Rsp to v n along least delay path True If True False Rsp is updated and sent to all neighbors except sending node True
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22 SLOW mode (cont) New member will receive set of responses –Selects one with least cost value –Assume selected one is (,SLOW,, ) –Sends request to – uses DCR to compute a path to satisfying delay constraint
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23 Example of DCDMR with SLOW Mode s VpVp VnVn Req Existing tree Least delay path VnVn VpVp s Rsp VnVn s VpVp
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24 DCDMR Algorithm Lemma –Let be any non-leaf node on T, is any child of on tree. If then
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25 Outline Motivation Network model and problem definition DCR algorithm DCDMR algorithm Performance evaluation Conclusion
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26 Performance Evaluation Compare performance with NAIVE and BSMA –NAIVE constructs dynamic tree only satisfy a given delay constraint –BSMA has best cost performance among all static multicast heuristics
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27 Simulation Parameters Random network –Link capacities is 155Mbps –average node degree=4 –Equivalent BW of background traffic on each link uniformly distributed between 10 and 120 Mbps –Random generated source s –Random series requests –Link costs Total currently reserved BW on link –Propagation speed on links is two thirds of light Queuing component is neglected
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28 First Case of Simulation Every in is add request –For DCDMR and NAIVE Generate new delay-constrained tree when join –For BSMA Directly generate T m for m members without considering request sequence –For simulation results (1) and (2) Delay bound is 50 ms
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29 Simulation Results (1)
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30 Simulation Results (2)
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31 Second Case of Simulation Request may be add or delete is considered How to determine next request? –Consider function : n : number of network nodes k : number of group nodes on current tree : 0.15 r : random number (0<r<1) : new request is delete or add if
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32 Simulation Results (3)
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33 Simulation Results (4)
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34 Conclusion Characteristics of DCDMR –Scales well Source needs small computation –Good cost performance In FAST mode, route computation is fast In SLOW mode, low cost tree is computed
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